Master cylinder for brakes



July 9, 1940- l.. E. LA BRIE I MASTER CAYLINDER FOR BRAKES Original Filed Nov. 2v2, 1930 vaste E.

'NZRb/ef 'Patented July 9, 1940 f UNITED -sTATas v.PATENT ortica inas'rria CYLINDER; manzanas Ludger a. la Brie, permit. met.,

Bendix' e Company, Sou corporatio ofvlllinoisk asoig'nor'to Original applicationLNovembcr 22, 1930, Serial No'. 497,383., Renewed October 12. 1936. Now

Patent No. 2,095,152, med october iz, 1932. Divided and this application June 9, 1937,

- serai No. 141,113

14 cam. w1. a02-54.0)A

This applic'ationis a division of my copending appncation serial No. 497,3s3,n1ed November 22,

1930, renewed October 12, 1936 and issued on October 12,1937, as Patent No. 2,095,752.

This invention relates tov brakes and is illustrated as embodied in a novel systemof lnrdraulic brakes for an automobile.

One'object of the invention is the provision of4 a master cylinder for a hydraulicbrake system m arranged with a valve which is automatically opened when the piston is returned to the released position.

A further object of the invention is the -provision of a master cylinder of such a hydraulic 15 brake system so arranged as to automatically f bleed the lines, i. e., filLthem with liquid and eliminate entrapped air.

The above and other, objects ofthe inventionl `and features including various novel and desirm able details of construction will be apparent from the following description of the illustrativeembodiments shown inthe accompanying drawing,

in which:

Figure 1 is a top plan view of part of an autou mobile chassis showing-the arrangement of the parts of the system of hydraulic brakes; and' Figure 2 is a section through the master cylinder assembly of Figure 1. i.

The chassis shownin Fig-ure 1 includes the usual chassis frame 30 supported by the usual springs on front and rear axles (not shown) carried bythe front wheels 32 having brakes indi'- cated geherally at 34 and on rear wheels 36 having chassis frame 30 with the outlet`42 of a masterI cylinder assembly 44 which-is shown more in 4 detail in Figure 2 and which contains an operating pistoncarried by a pisto rod 40 and thus connected with the usual brak pedal 48. The hydraulic system is kept full of liquid by means of a reservoir .S0-which is mounted on the dash above the master cylinder and on the bpposite side of the dash from the driver. Thereservoir 00 is connected to the mastercylinder 44 by means suchas a flexible conduit 52. -1 r The master cylinder indicated generally at 44 includes, as shown in Figure 2, a cylinder proper |00, which may be made as a casting and one J end of vwhich is permanently closed by a cap |08 containing the outlet .42 to the .conduit 40. In-

fside of the cylinder |00 is arranged a oating piston ||0 having a cylindrical extension |.|2 ipon which is sleeved va sealing member such as a rubber gasket |14 slidably engaging the inner face of thecyllnder |00,l The sealing member', ||4 is held in placeagainst the face of the piston I ||0by mean's such as a spring ||0 confined between the' sealing member ||2 and a washer or equivalent stop Ill on the forward end of the extension I |2. The piston-I |0 is urged in a direction to release the brakes by means such as a light spring |20 confined between the cap |03 and the stop at the end of the extension ||2.

.'Ihe qating piston ||0 is forced to the left to apply the brake by means such as a secondary axial opening through which the piston rod 40 passes and which is formed with a spherical seat receiving a spherical head |24on the end of the.

piston-rod. The spherical head |24 is embraced between the seat formed on the piston and the 'n semi-spherical concave bottom of a plug |20` threaded into the opening in the piston,\thus forming la ball-and-socket ioint. `rI'he idle or released position of the auxiliary piston |22 is determined by engagement of its base with a cup shaped stamping |20 threaded on the end of the cylinder |06 :lust beyond a angej|30 which is adapted to engage and be bolted to a part ofthe chassis frame of the car.

The auxiliary piston |22 is formed with an exso tension |32 disconnectedly engaging a projection |34.on the rear end ofthe piston ||0 so'that the piston |22 forces the floating piston |0` to the ieft toAaDply the brakes, but. des not compel the floating piston to return to its idle position 35 when the brakes are released'. The space |26 between the two pistons is in communication by a passage |30 with the conduit .52 from the liquid reservoir -so that any suction created by a quick return ofthe operating piston is compensated for o `provided mainly to insure that when the brakes are fully released.'l the oating piston ||'0l will iinallyvmove far enough to the right in Figure 3 to clear aDort Ina,Y communicating with the .conduit 02 through a passagewontrolledrby av 50 spring-pressed poppet valve |40 which is pushed upwardly y the conical return end of piston ||0 when the brake is' fully released.

Inl operating the master cylinder 44 for the application of the brakes, force exerted on the pedal 48 acts through the piston rod 48 and moves the pistons |22 and ||0 forward. The piston soon passes the port 38a and vforces liquid through the port 42 and the conduits 40 and 38 to the wheel cylinders and thus applies the brakes 34. Movement forward of the piston ||0 allows the valve to close. Because the valve |40 is closed by the first movement of the piston I0, it is unnecessary that the port |38a should be closed immediately. `When the applying forceis relieved from the pedal |48 the pistons |22 and ||0 are returned by the pressure of liquid acting on their forward faces. The pressure of the liquid reservoir 50 immediately forces the piston 22 rearwardly and as soon as preure is communicated from the wheel cylinder through the conduits 40 tothe front of the piston 0, that piston is also forced back. However, the piston 0 -is never drawn back by the movement of the piston |22 and therefore there is no suction created to draw in air in front of the piston ||0. On the complete return of the piston ||0 it raises the ,valve |40 to open the valve.

'I'he upward movement of the valve |40 establishes communication between the liquid in the reservoir and the space in the cylinder |06 in front of the oating piston |0 and thereby communicates 'the pressure in the liquid reservoir to the entire hydraulic system. As soon as the brake is applied, however, the piston ||0 cuts ot the port |38a and at the same time allows the valve |40 to seat itself to cut oi back pressure from the hydraulic system to the liquid reservoir and chamber |36. This, however, does not interfere with the free communication between lthe liquid reservoir and the space between the pistons ||0 and |22, which space therefore serves at `al1 times as a liquid seal effectively preventing any building up of suction anywhere in the assembly which might cause the introduction -of air.

While one illustrative embodiment of the invention has been described in detail, it is not my intention to limit the scope of the invention to that particular embodiment, or otherwise than by the terms -of the appended claims.

1. In hydraulic brake apparatus a master cylinder provided with a forward inlet port, a rearward inlet port and a passage connecting said ports, a. reservoir for a reserve supply of liquid,

a connection between said reservoir andrsaid rearward port, a check valve formed with a stem eX- tending into said master cylinder and positioned in said passage for at times preventing the passage of iiuid rearwardly through said passage, a seat for said valve, a oating piston in said master cylinder positioned lnormally at a point between said forward passage and said rearward passage and normally bearing upon said stern so as to raise said valve from its seat and to allow substantially free passage of liquid between said forward port and said rearward port, a spring bearing on'said valve and urging it towards its seat, a second piston in said master cylinder positioned rearwardly of both of saidinlet ports and normally bearing upon said oating piston.

2. In hydraulic brake apparatus a master cylinder provided with a forward inlet port, a rearward inlet port and a passage connecting said ports, a reservoir for a reserve supply of liquid, a connection between said reservoir and said rearward port,a check valve formed witha st em vextending into said master cylinder and positioned in said passage for at times-preventing the passage of iiuid rearwardly through said passage, a seat for said valve, a oating piston in said master cylinder positioned normally at a point between said forward passage and said rearward passage and normally bearing upon said stem so as to raise'said Ivalve from its seat and to allow substantially free passage of liquid between said forward port and said rearward port, a spring bearing on said valve and urging it towards its seat, a seond piston `in said master cylinder positioned rearwardly of `both of said inlet ports and normally bearing upon said floating piston, said check valve being closed upon movement of said forward piston so as to prevent rearward passage of liquid while allowing substantially free forward passage of liquid.

3. A brake operator comprising a master cylinvder formed with a brake applying outlet and a port and adapted `to hold liquid for applying brakes; a reservoir for providing'a reserve supply of liquid; a floating operating piston for applying braking pressure to the liquid in the cylinder, having a rearwardly-extending projection and normally positioned rearwardly of said port, but adapted to move forward over said port; a driver operated piston in the cylinder behind the first piston and disconnectedly engaging said projection; and means for maintaining said cylinder supplied with an adequate supply of liquid comprising a liquid connection from said reservoir continuously connected to said cylinder between said pistons, whereby the driver operated piston may be drawn back upon release of the brake while the'iioating piston is not necessarily drawn back and therefore there is no tendency-to suck in fluid from the brake applying outlet.

4. A brake operator comprising a master cylinder formed with a brake applying outlet and a port and adapted to hold liquid for applying brakes; a reservoir for providing a reserve supply of liquid; a iioating operating piston for applying braking pressure to the liquid in the cylinder and normally positioned rearwardly of said port, but

' adapted to move forward over said port; a driver operated Apiston in the cylinder behind the rst piston and disconnectedly engaging said piston; and means for maintaining said cylinder supplied with an adequate supply -of liquid comprising a liquid connection from said reservoir continuously connected to said cylinder between said pistons, whereby the driver operated piston may be drawn back as the brake is released without necessarily drawing back the floating piston and therefore there is no tendency to suck in iiui'd from the brake applying outlet.v

LUDGER E. LA BRIE. 

